Shale gas has become one of the most promising and fast-growing resources to supply the global energy needs in the foreseeable future. It is considered to be an unconventional resource because the gas is stored and “sealed” in pores of the source rock. The source rock typically has a low porosity (less than 10%) and an ultralow permeability (tens of nanodarcy), with significant amounts of the gas being stored in kerogen nanopores. To overcome the ultralow permeability and enable production of economic quantities of hydrocarbons, stimulation techniques such as hydraulic fracturing are usually required.
Unfortunately, shale gas storage mechanisms still remain poorly understood, often resulting in inaccurate estimation of original gas in-place (OGIP) within the reservoir. Existing laboratory techniques that were designed for use with conventional resources fail to provide accurate measurements for characterizing source rocks because of low permeability and porosity. Moreover, some of these techniques are destructive to the samples and others are very time consuming. For example, gas storage mechanisms can often be determined from adsorption isotherm measurements. These measurements are traditionally acquired using volumetric or gravimetric methods that have proven to be insensitive to the adsorbed or confined phase of gas in the nanometer-sized pores typical of shale. In general, these conventional techniques are unsuitable to meet the challenge of the current market needs.